I'm a huge fan of growing arugula in containers. It is incredibly easy to grow and is one of the spiciest and most delicious greens available. I also recently discovered that arugula flowers are stunningly beautiful and one of the best tasting edible flowers out there.
Choosing a container - Since the roots of arugula are relatively shallow, you don't need a giant, or particularly deep container. However, you'll want to plant a fair amount of arugula, because once you get a taste for it, you might find you're eating a lot of it.

Though you can grow arugula in almost anything,a self-watering container works particularly well.
Planting Arugula - Like most salad greens, arugula seeds are tiny, so you have to be careful not to plant them too deep. I fill my garden pot up with potting mix, then gently flatten it out with my hand. I then distribute the seeds as uniformly as possible onto the potting mix. I then take my flat palm and gently pat the seeds onto the soil. You can then cover them lightly with potting soil, or I like to put a thin layer of seed starting mix over the seeds, gently patting again. Add water very carefully, either using a rose attachment, or a gentle spray from the hose. You don't want the water pressure or weight to disturb your seeds. Plant in full sun, or for a longer season, give arugula mid day shade.

Growing Arugala - Arugula doesn't love hot weather and gets quite bitter if grown when it's steaming hot outside. Start arugula seeds as soon as danger of frost is over, this is a great plant to sow once a week or every two weeks to keep a constant supply.

Keep the soil evenly moist until seedlings emerge, which will take from 7 to 14 days. Thin seedlings so they are one to three inches apart, when they are about an inch or two tall. These young leaves are some of the tenderest and most delicious, so add them to your salad.

Harvesting Arugala - Your arugula should be full grown and ready to harvest in about three to four weeks. The younger the leaves, the more tender and sweet they will be, so don't wait too long to start picking them. Once the seedlings are 3 to 4 inches long you can either pull out the whole plant or, if you want the plants to continue to grow, you can collect just the leaves by cutting or tearing them off towards their base.

Arugula Flowers - I think the flowers are the best part of the arugula - they aren't as spicy as the leaves and are a little sweet. The flowers appear after the leaves have grown to full size and are too bitter to eat. If you don't harvest your arugula, you should see flowers. Pick them off and eat them or add them to a salad or an open-faced sandwich for a beautiful treat. I grow some arugula for the flowers alone.

Larger image of arugula flowers.